It seems counter-intuitive, but introverts and closet introverts populate the highest corporate offices, so much so that four in 10 top executives test out to be introverts, a proportion only a little lower than the 50-50 split among the overall population age 40 and older.

The list of well-known corporate CEO introverts reads like a Who's Who, starting with Gates, who has long been described as shy and unsocial, and who often goes off by himself to reflect. Others widely presumed to be introverts include Warren Buffett, Charles Schwab, movie magnate Steven Spielberg and Sara Lee CEO Brenda Barnes.

Jim Collins, in his 2001 bestseller Good to Great, was one of the first to dispel conventional wisdom that successful leaders climb to the top because they're naturally outgoing. He found that the most successful companies rarely had so-called celebrity CEOs, but rather had CEOs who were self-effacing and humble to a fault. Charisma was a handicap, he concluded.

In some organizations introverts might not rise because they are seen as uninspiring, but the same personality trait is embraced elsewhere as calm, unemotional and wise. Scherpenseel says he often stays quiet at meetings while others debate into exhaustion. When he finally weighs in, the room falls quiet with attention.